Conventionally, a pressure sensor has been used to detect the pressure of liquid flowing in a flow path. As such a pressure sensor, there is known a single-port type pressure sensor which introduces liquid from a main flow path, in which the liquid is flowing, into an introduction flow path, and detects the pressure of the introduced liquid (see, for example, Patent Literature 1).
When the pressure of the liquid which is introduced from the main flow path is detected via a pressure sensitive part (pressure receiving surface) of a sensor element, if the pressure sensor is configured such that the liquid comes into direct contact with the pressure sensitive part, there is a risk that a part of the pressure receiving surface or a sealing member, such as an O-ring, which is brought into contact with the pressure receiving surface, dissolves due to the effect of the liquid (for example, a corrosive solution) and thereby contaminates the liquid flowing in the main flow path.
Patent Literature 1 discloses a pressure sensor in which a diaphragm part for isolating the contact between the liquid and the sensor element is provided at an end part of a fluid introduction part (introduction flow path) so that the pressure of the liquid is transferred to a pressure sensitive part via the diaphragm part.